Am Montag, den 25.05.2020, 10:33 +0000 schrieb Dridi Boukelmoune: > On Sun, May 24, 2020 at 8:12 AM Geoff Simmons <[email protected]> wrote: > > On 5/24/20 01:29, [email protected] wrote: > > > This notes > > > > > > https://varnish-cache.org/docs/trunk/installation/platformnotes.html > > > > > > has a comment about "Transparent hugepages". > > > > > > Does this still apply to EL8? > > > > That's a good heads-up that those docs need to be updated -- they > > refer > > to RHEL6 and Linux kernel 3.2. If I'm not mistaken, enabling THP by > > default was fairly new at the time, but it's still the default and > > that's old news now, as your settings confirmed (just checked that > > it's > > also the default on my Debian stretch laptop). > > > > The issue is not really the distro or kernel version, but the use > > of the > > THP feature, and it's still a problem, probably always will be. > > AFAICT > > THP does nothing good for Varnish. It's harmless if you're lucky, > > but it > > can be very disruptive. > > > > I haven't tried it with RHEL8. The doc says that it "is known to > > cause > > sporadic crashes of Varnish", but while I haven't seen crashes, on > > RHEL7 > > I've seen that the memory usage of the cache process bloats up > > enormously, orders of magnitude larger than the actual size of the > > cache > > and anything else in Varnish that occupies memory. After disabling > > THP > > for Varnish (as detailed below), I saw memory usage become much > > smaller, > > more like what you'd expect from the cache size and other overhead. > > > > There's an explanation for why THP causes that, but suffice it to > > say > > that THP creates trouble for a variety of apps that manage a lot of > > memory. MongoDB, Oracle, redis and many other projects advise you > > to > > turn it off. THP is inevitably a problem for the jemalloc memory > > allocator, which is invariably used with Varnish. > > I just wanted to react to the "invariably" word here. This is not > accurate, it should read "by default" instead. > > See ./configure --help: > > > --with-jemalloc use jemalloc memory allocator. Default is yes on > > Linux, no elsewhere > > And considering that jemalloc is not available in el8, but epel8 > instead. I suspect Red Hat ships a varnish package that uses glibc > with no custom allocator. >
Seems so: # strings /usr/sbin/varnishd | grep -i jemalloc <empty> and comparing with redis that is also in the distribution base repo: # strings /usr/bin/redis-server|grep -i jemalloc|head -4 je_jemalloc_prefork je_jemalloc_postfork_child je_jemalloc_postfork_parent jemalloc-5.1.0 are the implications that varnish build that way in this context is more resilient with hugepages enabled? -- Leon _______________________________________________ varnish-misc mailing list [email protected] https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
